1. Field of the Invention
This invention relates to a circuit interrupter operating mechanism, and more particularly, it pertains to a mechanism for feeding a gas to a piston-cylinder drive mechanism for opening and closing contacts in a circuit interrupter such as an oil circuit breaker.
2. Description of the Prior Art
Certain types of circuit interrupters, such as the so-called "puffer" circuit breaker, have involved relatively slow contact-opening time periods. Attempts to reduce the opening times have met with some success. For example, U.S. Pat. Nos. 2,096,619, 2,436,194, 2,476,024 and 2,552,358 disclose typical means for expediting the opening and/or closing of contacts in circuit breakers.
Inasmuch as circuit breakers of this type involve the use of various mechanical linkage systems, it is necessary to initiate movement of the system as soon as possible when an overcurrent occurs. At such times, most mechanical devices for initiating the opening of contacts, have been unsatisfactory due to the time lost in applying forces once the signal to open occurs. Indeed, most recent innovations using electrical ignition, although usually faster, still involve an ignition time which is slower than desirable. Thus, the so-called "bridge-wire" type of primer, comprising a resistance wire which directly or indirectly ignites a propellant, involves an ignition time of one to three milliseconds. Faster ignition times are desirable in order to open contacts when overcurrents occur.
Associated with the foregoing is the phenomenon of certain types of power circuit breakers operating through an "open-close-open" or "close-open-close" duty cycle in a fast sequence. For example, when a circuit breaker opens, it can immediately reclose and will stay closed where an overcurrent such as a short circuit clears before it recloses. However, where a short circuit continues, the circuit breaker will immediately open again, thus completing the open-close-open duty cycle. However, a circuit breaker may have the close-open-close duty cycle whereupon the foregoing procedure is reversed. One problem inherent in such duty cycles is the use of ancillary means for actuating a cylinder and piston mechanism that opens and closes the contacts. More particularly, the time for the piston to move through one motion is the time allowed for the ancillary means to prepare for the next function resulting in either the opening or closing of the contacts. Most ancillary means of prior construction have limited the duty cycle operation time.
Finally, the conventional pneumatic cylinder and piston mechanism for opening and closing the contacts of a circuit interrupter have been of the low pressure type which operates at from 100 to 1000 psi. In order to facilitate the opening and closing of the contacts of the circuit interrupter, most propellants currently available for operating the cylinder-piston mechanisms operate at very high pressures of about 6000 psi to enable the propellant to burn. This large pressure results in lower gas volume requirements; thus, flow time necessary for operation is much improved.